1. Field of the Invention
This invention relates to encapsulated spring assemblies and more particularly to a punch press assembly having a preloaded encapsulated spring element.
2. Prior Art
Springs are used extensively in punching set ups for applying a force to a punch guide, or for separating the work piece from the die. Additionally, such springs are well-known in other machine environments where they may be used to bias two relatively movable members towards or away from one another. In certain instances it has been known to encase the spring in a protective housing either for safety purposes or to prevent the spring from being adversely affected by dirt and the like. Moreover, it is known in certain devices to provide a pre-load on a spring. For example, where springs are used between a housing and a part partially received in the housing and partially projectable from the housing, it is known to pre-load the spring at the time the part is assembled into the housing such that a desired initial bias is provided to the part.
Additionally, in the punching art, it has been known to provide punch assemblies wherein the punch is provided with a punch return spring or with a punch guide spring wherein the spring may be pre-loaded by the provision, for example, of an adjustable head on the punch.